Messages in this thread Patch in this message |  | | | Subject | [PATCH] Avoid unncessary checksum validation in TCP/UDP netfilter | | Date | Fri, 27 May 2005 12:03:08 +0100 | | From | Keir Fraser <> |
| |
The TCP/UDP connection-tracking code in netfilter validates the checksum of incoming packets, to prevent nastier errors further down the road. This check is unnecessary if the skb is marked as CHECKSUM_UNNECESSARY.
This patch will improve performance for networkinterfaces that perform CHECKSUM_UNNECESSARY-style checksum offload (that's most modern ones). More importantly (for me :-)) is that this makes netfilter play nicely with checksum avoidance in the Xen virtual machine monitor. Inter-domain traffic has no checksum calculated, so validation checks will fail even though the packet data is good. Of course, this avoidance relies on the network stack respecting CHECKSUM_UNNECESSARY.
Signed-off-by: Keir Fraser <Keir.Fraser@xl.cam.ac.uk>
diff -ur linux-2.6.11/net/ipv4/netfilter/ip_conntrack_proto_tcp.c linux-2.6.11-csum/net/ipv4/netfilter/ip_conntrack_proto_tcp.c --- linux-2.6.11/net/ipv4/netfilter/ip_conntrack_proto_tcp.c 2005-05-27 11:47:48 +01:00 +++ linux-2.6.11-csum/net/ipv4/netfilter/ip_conntrack_proto_tcp.c 2005-05-27 11:48:07 +01:00 @@ -803,6 +803,7 @@ */ /* FIXME: Source route IP option packets --RR */ if (hooknum == NF_IP_PRE_ROUTING + && skb->ip_summed != CHECKSUM_UNNECESSARY && csum_tcpudp_magic(iph->saddr, iph->daddr, tcplen, IPPROTO_TCP, skb->ip_summed == CHECKSUM_HW ? skb->csum : skb_checksum(skb, iph->ihl*4, tcplen, 0))) { diff -ur linux-2.6.11/net/ipv4/netfilter/ip_conntrack_proto_udp.c linux-2.6.11-csum/net/ipv4/netfilter/ip_conntrack_proto_udp.c --- linux-2.6.11/net/ipv4/netfilter/ip_conntrack_proto_udp.c 2005-05-27 11:47:48 +01:00 +++ linux-2.6.11-csum/net/ipv4/netfilter/ip_conntrack_proto_udp.c 2005-05-27 11:48:07 +01:00 @@ -120,6 +120,7 @@ * and moreover root might send raw packets. * FIXME: Source route IP option packets --RR */ if (hooknum == NF_IP_PRE_ROUTING + && skb->ip_summed != CHECKSUM_UNNECESSARY && csum_tcpudp_magic(iph->saddr, iph->daddr, udplen, IPPROTO_UDP, skb->ip_summed == CHECKSUM_HW ? skb->csum : skb_checksum(skb, iph->ihl*4, udplen, 0))) { |  |